Hot-carriers refer to holes or electrons that have gained very high kinetic energy in areas of high electrical field intensity within a semiconductor device (e.g., a metal-oxide semiconductor (MOS) device). Because of their high kinetic energy, hot carriers can get trapped in device areas (e.g., the gate oxide, the silicon-oxide interface, etc.) where they should not be, which can cause changes to the device threshold voltage and diminish device lifetime. Stacked MOS devices have been widely used in over-drive circuits to reduce hot-carrier degradation and reliability effects. In many approaches, however, voltage Vds, the voltage drop across the drain and the source of a MOS (e.g., the first MOS in a pair of stacked MOS devices) still experiences a high over-voltage during a gate signal transition (e.g., a transition from a low voltage level to a high voltage level or from a high voltage level to a low voltage level), which continues to cause hot-carrier degradations.
Like reference symbols in the various drawings indicate like elements.